Wish there was a license attached to it. I didn't see one in a file or attached as a header to any of the code. Without knowing what the license is, this project is not overly useful to anyone but the creator.
Why the sigh? It's a sign that PHP is maturing and that PHP is becoming much more component based, which is good. Composer is at the core of all this and it's a big win for the PHP landscape, no doubt.
Instead of creating another framework , make a service provider/controller and make your library pluggable with any Silex application. Sorry but silex is ultra pluggable , so dont force people into something. Silex Di is here to help and you should provide hooks instead of making decisions on everything.
There should not be any app.php file in your project. Unless you need to extend the silex Application class (you shouldn' need to), write a service provider or a generic controler.
It should be a library usable with any silex app , just like Symfony and its bundles.